JP2002054511A - Egr cooler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve heat exchange efficiency of an EGR cooler, by increasing a heat transfer area in an internal/external peripheral surface of a tube. SOLUTION: Relating to this EGR cooler, having a tube 3 and a shell enveloping this tube 3 to supply cooling water 9 to and discharge it from the inside of this shell to additionally make exhaust gas 10 pass through in this tube 3 so as to perform a heat exchange between this exhaust gas 10 and the cooling water 9, ring-state fins 11, as a fin shape increasing a heat transfer area, are formed in multi-steps by a relatively short pitch in an external peripheral surface of the tube 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an EGR cooler which is attached to an EGR device for recirculating exhaust gas of an engine to reduce the generation of nitrogen oxides and cools the exhaust gas for recirculation.

[0002]

2. Description of the Related Art Conventionally, an EGR device for reducing the generation of nitrogen oxides by recirculating a part of exhaust gas from an engine of an automobile or the like to the engine has been known.
In the device, when the exhaust gas recirculated to the engine is cooled, the temperature of the exhaust gas is reduced and its volume is reduced, so that the combustion temperature is reduced without significantly lowering the output of the engine and the nitrogen oxidation is effectively performed. In order to reduce the generation of substances, some engines are equipped with an EGR cooler for cooling the exhaust gas in the middle of a line for recirculating the exhaust gas to the engine.

FIG. 8 is a cross-sectional view showing an example of the EGR cooler. In the figure, reference numeral 1 denotes a cylindrical shell, and at both ends in the axial direction of the shell 1, the end faces of the shell 1 are closed. The plates 2 and 2 are fixed to each other, and both ends of a large number of tubes 3 are fixed to the respective plates 2 and 2 in a penetrating state.
Extends in the axial direction.

In the vicinity of one end of the shell 1,
A cooling water inlet pipe 4 is attached from the outside, and a cooling water outlet pipe 5 is attached from the outside near the other end of the shell 1, and cooling water 9 flows from the cooling water inlet pipe 4 into the shell 1. The supplied water flows outside the tube 3 and is discharged from the cooling water outlet pipe 5 to the outside of the shell 1.

Further, bonnets 6 and 6 formed in a bowl shape are fixed to the opposite sides of the shells 1 of the plates 2 and 2 so as to cover the end faces of the plates 2 and 2, respectively. The exhaust gas inlet 7 is provided at the center of the bonnet 6, and the exhaust gas outlet 8 is provided at the center of the other bonnet 6, respectively.
After the exhaust gas 10 of the engine enters the inside of one bonnet 6 from the exhaust gas inlet 7 and is cooled by heat exchange with the cooling water 9 flowing outside the tubes 3 while passing through a number of tubes 3, the other one is cooled. The exhaust gas is discharged into the bonnet 6 and recirculated from the exhaust gas outlet 8 to the engine.

In the drawing, reference numeral 5a denotes a bypass outlet pipe provided at a position facing the cooling water inlet pipe 4 in the diametrical direction of the shell 1, and a part of the cooling water 9 is extracted from the bypass outlet pipe 5a. The stagnation of the cooling water 9 is prevented from occurring at a position facing the cooling water inlet pipe 4.

[0007]

However, in such a conventional EGR cooler, since the tube 3 is formed of a smooth tube, the heat transfer area on the outer peripheral surface and the inner peripheral surface of the tube 3 is small, and the exhaust gas There is a problem that the heat exchange efficiency between the cooling water 10 and the cooling water 9 is poor.

The present invention has been made in view of the above circumstances, and has as its object to increase the heat transfer area on the outer peripheral surface and the inner peripheral surface of a tube to improve the heat exchange efficiency of an EGR cooler.

[0009]

SUMMARY OF THE INVENTION The present invention comprises a tube,
A shell surrounding the tube, wherein cooling water is supplied and discharged inside the shell, and exhaust gas is passed through the tube to exchange heat between the exhaust gas and the cooling water.
A GR cooler characterized in that at least one of an outer peripheral surface and an inner peripheral surface of the tube has a fin shape for increasing a heat transfer area.

Here, as the fin shape for increasing the heat transfer area, a ring-shaped fin, a rack-shaped fin, a protruding fin, a straight fin extending in the longitudinal direction of the tube, or the like is appropriately selected, and the outer peripheral surface of the tube or the inner fin is formed. It can be formed on the peripheral surface.

According to this structure, the heat transfer area on the outer peripheral surface and the inner peripheral surface of the tube is increased by providing the fin shape on the outer peripheral surface and the inner peripheral surface of the tube. The heat exchange efficiency of the tube is greatly improved, and especially when the inner peripheral surface of the tube has a fin shape, the exhaust gas flow along the inner peripheral surface of the tube is positively turbulent due to the fin shape. It is possible to increase the frequency of contact with the inner peripheral surface of the tube,
The heat exchange efficiency of the GR cooler is further improved.

Further, the present invention comprises a tube and a shell surrounding the tube, and supplies and discharges cooling water to the inside of the shell and passes exhaust gas and the cooling water through the exhaust gas into the tube. An EGR cooler adapted to perform heat exchange, wherein a molded fin for increasing a heat transfer area is fitted inside the tube.

Here, as the forming fin for increasing the heat transfer area, a forming fin having a radial cross section that divides the inside of the tube into a plurality of channels can be adopted and fitted inside the tube.

In this case, since the heat transfer area on the inner peripheral surface of the tube is increased by fitting the forming fin inside the tube, the heat exchange efficiency of the EGR cooler is reduced. Since the flow rate of the exhaust gas flowing through the tube can be greatly improved, and the flow rate of the exhaust gas flowing through the tube can be positively turbulent by the forming fins, and the frequency of contact with the inner peripheral surface of the tube can be increased. The heat exchange efficiency of the cooler is further improved.

Further, the present invention comprises a tube and a shell surrounding the tube, wherein cooling water is supplied / discharged inside the shell, and exhaust gas is passed through the tube so that the exhaust gas and the cooling water are separated from each other. An EGR cooler adapted to perform heat exchange, characterized in that the tube itself is deformed to have irregularities on an outer peripheral surface and an inner peripheral surface of the tube to increase a heat transfer area.

Here, as the concavo-convex shape for increasing the heat transfer area, it is possible to twist the tube to form a twisted shape having corrugated concavities and convexities on the outer peripheral surface and the inner peripheral surface of the tube.

In such a case, the tube itself is deformed to form irregularities on the outer and inner peripheral surfaces of the tube, so that the transmission on the outer and inner peripheral surfaces of the tube is improved. Since the heat area is increased, the heat exchange efficiency of the EGR cooler is greatly improved, and the uneven shape on the inner peripheral surface side appears as a reversed shape of the flow of the exhaust gas flowing through the tube on the outer peripheral surface side. As a result, it becomes possible to increase the frequency of contact with the inner peripheral surface of the tube by positively causing turbulence, so that the heat exchange efficiency of the EGR cooler is further improved.

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view showing a first embodiment of the present invention in which a part is cut obliquely, and the portions denoted by the same reference numerals as those in FIG. 8 represent the same components.

In the first embodiment shown here, a heat transfer area is provided at a plurality of longitudinal positions on the outer peripheral surface of an EGR cooler having substantially the same configuration as the EGR cooler described above with reference to FIG. As the fin shape to be increased, a tube 3 in which ring-shaped fins 11 are formed in multiple stages at a relatively short pitch is adopted.

FIG. 2 is a perspective view showing a second embodiment of the present invention in a state where a part is cut obliquely. To
As the fin shape for increasing the heat transfer area, a plurality of rack-shaped fins 12 extending in the longitudinal direction are formed by cutting teeth of the same shape at equal intervals, and the parallel grooves 13 extending in the longitudinal direction between the rack-shaped fins 12 are formed. Is formed.

FIG. 3 is a perspective view showing a third embodiment of the present invention in a state where a part of the third embodiment is cut obliquely. In the example shown in FIG. A large number of protruding fins 14 are
And a tube 3 having a twisted projection 15 also formed on the inner peripheral surface thereof.

FIG. 4 is a perspective view showing a fourth embodiment of the present invention in which a part is cut obliquely. In the example shown here, a plurality of circumferential portions are formed on the inner peripheral surface. In addition, a tube 3 having a large number of straight fins 16 extending in a longitudinal direction is adopted as a fin shape for increasing a heat transfer area.

When the tube 3 as shown in FIGS. 1, 2 and 3 is employed in the EGR cooler, the ring-shaped fin 11, the rack-shaped fin 12, the projection-shaped By providing the fin shape such as the fin 14, the heat transfer area with the cooling water 9 on the outer peripheral surface of the tube 3 is increased, so that the heat exchange efficiency of the EGR cooler is greatly improved. As shown in
When the torsion projection 15 is also provided with a fin shape on the inner peripheral surface of the tube 3, the flow of the exhaust gas 10 along the inner peripheral surface of the tube 3 is turbulently positively swirled by the torsion projection 15. As a result, the frequency of contact with the inner peripheral surface of the tube 3 can be increased.
The heat exchange efficiency of the GR cooler is further improved.

Further, the tube 3 as shown in FIG.
If it is adopted for a cooler, the heat transfer area between the inner peripheral surface of the tube 3 and the exhaust gas 10 is increased by attaching the straight fins 16 extending in the longitudinal direction to the inner peripheral surface of the tube 3 in a fin shape. Therefore, the heat exchange efficiency of the EGR cooler is greatly improved, and the flow of the exhaust gas 10 along the inner peripheral surface of the tube 3 is reduced by the straight fins 16 as in the case of FIG. Turbulence while minimizing the EGR, it is possible to increase the frequency of contact with the inner peripheral surface of the tube 3.
The heat exchange efficiency of the cooler is further improved.

FIG. 5 is a perspective view showing a fifth embodiment of the present invention with a part thereof cut off obliquely. In the example shown here, forming fins 17 having a radial cross section are provided inside. The fitted tube 3 is adopted, and the inside of the tube 3 is divided into a plurality of flow paths 18 by the forming fins 17. The surface of the forming fin 17 has a number of parallel grooves 1 extending in the longitudinal direction of the tube 3.
9 are formed.

FIG. 6 is a perspective view showing a sixth embodiment of the present invention in which a part is cut off obliquely. In the example shown here, a radial cross section similar to FIG. Are formed so as to form a petal-shaped radial cross-section by alternately folding a metal sheet. In this case as well, the inside of the tube 3 is divided into a plurality of flow paths 18 by the forming fins 20. Is the same.

When the tube 3 as shown in FIGS. 5 and 6 is used for the EGR cooler, the forming fin 17 and the forming fin 20 are fitted into the tube 3 so that the inside of the tube 3 Since the heat transfer area on the peripheral surface is increased, the heat exchange efficiency of the EGR cooler is greatly improved, and the flow of the exhaust gas 10 flowing through the tube 3 is positively increased by the forming fins 17 and 20. Since it becomes possible to increase the frequency of contact with the inner peripheral surface of the tube 3 by turbulent flow, the heat exchange efficiency of the EGR cooler is further improved.

FIG. 7 is a perspective view showing a seventh embodiment of the present invention in which a part is cut obliquely. In the example shown here, the tube 3 itself is deformed and processed. The outer peripheral surface and the inner peripheral surface of the tube 3 are provided with a concavo-convex shape for increasing a heat transfer area. More specifically, the tube 3 is formed by twisting the tube 3 made of a normal smooth tube. Shape with corrugations on the outer and inner peripheral surfaces
1 and 22 are formed.

When the tube 3 as shown in FIG. 7 is employed for the EGR cooler, the tube 3 is subjected to a torsion deformation process so that the outer peripheral surface and the inner peripheral surface of the tube 3 have a twisted shape 2.
Since the heat transfer area on the outer peripheral surface and the inner peripheral surface of the tube 3 is increased by adding the components 1 and 22, the heat exchange efficiency of the EGR cooler is greatly improved.
The flow of the exhaust gas 10 flowing in the tube 3 is positively turbulently generated by the twisted shape 22 on the inner peripheral surface side, which appears as an inverted shape of the twisted shape 21 on the outer peripheral surface side, thereby reducing the frequency of contact with the inner peripheral surface of the tube 3. Since it is possible to increase the heat exchange efficiency, the heat exchange efficiency of the EGR cooler is further improved.

It should be noted that the EGR cooler of the present invention is not limited to the above-described embodiment, and that fin shapes, formed fins, and uneven shapes other than those shown in the drawings can be adopted. In addition, it goes without saying that various changes can be made without departing from the spirit of the present invention.

[0032]

As described above, according to the EGR cooler of the present invention, the heat transfer area on the outer peripheral surface and the inner peripheral surface of the tube can be increased, so that the heat exchange efficiency of the EGR cooler is greatly improved. In particular, when a fin shape, a molded fin, and a concavo-convex shape are applied to the inner peripheral surface of the tube, the flow of exhaust gas flowing through the tube is positively turbulent. The frequency of contact with the inner peripheral surface of the tube can be increased by
An excellent effect that the heat exchange efficiency of the GR cooler can be further improved can be obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a first embodiment of the present invention in which a part is cut off obliquely.

FIG. 2 is a perspective view showing a second embodiment of the present invention in which a part is cut obliquely.

FIG. 3 is a perspective view showing a third embodiment of the present invention in which a part is cut off obliquely.

FIG. 4 is a perspective view showing a fourth embodiment of the present invention, with a part thereof cut off obliquely.

FIG. 5 is a perspective view showing a fifth embodiment of the present invention by cutting a part of the fifth embodiment diagonally.

FIG. 6 is a perspective view showing a sixth embodiment of the present invention in which a part is cut obliquely.

FIG. 7 is a perspective view showing a seventh embodiment of the present invention in which a part is cut obliquely.

FIG. 8 is a sectional view showing an example of a conventional EGR cooler.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Shell 3 Tube 9 Cooling water 10 Exhaust gas 11 Ring-shaped fin (fin shape) 12 Rack-shaped fin (fin shape) 14 Projection fin (fin shape) 15 Twisting projection (fin shape) 16 Straight fin (fin shape) 17 Forming fin 18 Flow path 20 Forming fin 21 Twisted shape (irregular shape) 22 Twisted shape (irregular shape)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F28F 1/40 F28F 1/40 A 1/42 1/42 A

Claims (9)

[Claims] 1. A cooling system comprising: a tube; and a shell surrounding the tube, wherein cooling water is supplied to and discharged from the inside of the shell, and exhaust gas is passed through the tube to exchange heat between the exhaust gas and the cooling water. An EGR cooler characterized in that at least one of an outer peripheral surface and an inner peripheral surface of the tube has a fin shape for increasing a heat transfer area. 2. The EG according to claim 1, wherein a ring-shaped fin is formed at least on an outer peripheral surface of the tube.
R cooler. 3. The EG according to claim 1, wherein a rack-like fin is formed on at least an outer peripheral surface of the tube.
R cooler. 4. The EGR according to claim 1, wherein a protruding fin is formed on at least an outer peripheral surface of the tube.
Cooler. 5. The EGR cooler according to claim 1, wherein straight fins extending in a longitudinal direction of the tube are formed on at least an inner peripheral surface of the tube. 6. A tube, comprising a shell surrounding the tube, for supplying and discharging cooling water to the inside of the shell and passing exhaust gas into the tube to exchange heat between the exhaust gas and the cooling water. An EGR cooler according to any one of claims 1 to 3, wherein a molded fin for increasing a heat transfer area is fitted inside the tube. 7. The EGR cooler according to claim 6, wherein a molded fin having a radial cross section that divides the inside of the tube into a plurality of flow paths is fitted. 8. A cooling apparatus comprising: a tube; and a shell surrounding the tube, for supplying and discharging cooling water inside the shell and passing exhaust gas into the tube to exchange heat between the exhaust gas and the cooling water. An EGR cooler, characterized in that the tube itself is deformed and the outer peripheral surface and the inner peripheral surface of the tube are provided with irregularities to increase a heat transfer area. 9. The EGR cooler according to claim 8, wherein the tube is twisted to form a twisted shape having corrugations on the outer peripheral surface and the inner peripheral surface of the tube.